In the performance of vascular intervention procedures, guiding catheters are routinely used to guide medical instruments and/or radiopaque contrast media into a selected blood vessel. For example, guiding catheters can be used to guide balloon-tip catheters (i.e., for coronary angioplasty procedures) and atherectomy instruments (i.e., for coronary atherectomy procedures) through the femoral artery of a patient for access to the coronary arteries via the ascending and descending aorta.
Guiding catheters typically comprise an elongated, torque-transmitting, tubular member open at both ends and having perfusion ports in a sidewall thereof. Such perfusion ports are usually located within about 3 centimeters of the distal tip such that, when the distal tip is seated in, for example, an ostium of a coronary artery, blood can enter the perfusion ports from the aorta and pass through the lumen of the guiding catheter and out the distal tip to perfuse the selected coronary artery.
Proper positioning of a guiding catheter in the selected coronary artery is an important aspect of successful coronary interventions. Briefly, this involves inserting the guiding catheter into the femoral artery, feeding the guiding catheter into the ascending aorta, and seating the distal tip in the appropriate coronary ostium. Insertion of a guiding catheter into a femoral artery can be accomplished by a standard percutaneous catheter introduction technique, such as by the use of a catheter introducer which is inserted into the femoral artery using the Seldinger technique. Feeding the guiding catheter into the ascending aorta typically involves passing (e.g., over a guidewire) a sufficient length (e.g., about 80 cm) of the catheter into the femoral artery until the distal tip completes its travel up the descending aorta and down the ascending aorta. In order to properly seat the distal tip of the guiding catheter into the selected coronary ostium, the physician typically repeatedly injects radiopaque contrast media and, by viewing the contrast media flow on an x-ray monitor (e.g., a fluoroscope) while manipulating the catheter distal tip, gradually seats the distal tip.
When seating the distal tip in the selected coronary ostium, it can be appreciated that it would be beneficial to have the ability to sense (i.e., by the physician, at the proximal end of the tubular member) when the distal tip is improperly seated against the aortic wall (e.g., when the distal tip is at least partially obstructed by the aortic wall). In many instances, this would significantly reduce the number of contrast media injections needed to properly seat the catheter, thereby saving time and contrast media. When seating catheters without perfusion ports, such sensing can be accomplished by sensing the damping of the blood pressure wave in the lumen of the guiding catheter which would accompany the blocking of the distal tip (e.g., by sensing pressure fluctuations in the lumen utilizing a pressure sensor at the proximal end of the catheter). However, when using known catheters with perfusion ports, the damping of the blood pressure wave generally does not occur because the perfusion ports remain open when the distal tip is seated against the aortic wall.
Once the distal tip has been properly seated in the selected coronary ostium, contrast media is typically injected through the lumen of the catheter and into the artery so that the position of the obstruction (e.g., atherosclerosis) within the selected coronary artery can be viewed on an x-ray monitor. Further, once the intervention procedure has been performed, contrast media can be injected to assess the results of the intervention. With many known devices, the presence of perfusion ports impairs the ability to effectively inject high concentrations of contrast media into the artery because a portion of the contrast media can exit the guiding catheter lumen through the perfusion ports and can be dispersed with blood flow in the ascending aorta. It can be appreciated that such dispersal with aortic blood can significantly increase the amount of contrast media required for adequate visualization of the selected artery. In this regard, dispersal of large amounts of contrast media can result in disruption of kidney functions or cause other complications.